The invention relates to a motor vehicle with an electric motor, an on-board high-voltage power supply, and several energy stores, for examples high-voltage batteries which form a multi-battery system and are provided to supply energy to an electric drive motor, with the multi-battery system being connected via a switching unit with an inverter that controls the electric motor. The switching unit separates hereby this multi-battery system galvantically from the on-board high-voltage power supply. The invention also relates to a method of operating the motor vehicle.
An on-board high-voltage power supply and a high-voltage energy store are typically provided in an electric vehicle, such as, for example, a hybrid vehicle or a battery-powered vehicle.
High-voltage batteries in electrical and hybrid vehicles have a storage capacity (in ampere hours) and a high-volt voltage, involving here an electrical voltage of greater than 60 volts, particularly greater than 100 volts, the product of which establishing the energy and thus the range that can be achieved with this battery. The maximum voltage is limited by the semiconductor components in the power electronics, and the capacity by the cell capacity. A further increase of the cell capacity makes them potentially more unsafe. Another solution involves the parallel connection of the cells in the battery and thus increase of the capacity.
It has been considered disadvantageous in the art that a parallel connection of the cells leads to compensating currents between the cells connected in parallel and thus to energy losses. Therefor, such circuits are undesirable.
DE 10 2009 042 001 A1 describes a vehicle with an electric drive and a battery, and having a receiving device for a second battery. The supply of electric drive can be assumed by both the one battery and the other battery. The two batteries can each be charged and discharged via a control device. A central control unit determines a desired target signal which determines the route with the aid of a navigation system and the driver's destination input. The central control unit decides which of the two batteries is used for the route on the basis of these data and data based on the remaining storage capacities of the batteries as transmitted from the battery control devices.
DE 10 2010 038 886 A1 discloses a distributed battery system for motor vehicles, in which at least two spatially separate battery modules and a central battery control unit are provided for monitoring.
The disadvantage of the mentioned battery systems, however, is that during a travel cycle only one battery is available, i.e. decision must be made before departure as to which battery has the needed state of charge for reaching the destination. Accordingly, one of the two batteries is assigned to the drive. If neither of these batteries has sufficient capacities for reaching the destination, the central control device schedules travel stops at charging stations or battery exchange stations. When the central control unit is not aware of the length of the route, the battery with greater storage capacity is automatically made available. The driver thus has to stop the vehicle in order to change the driving mode from one battery to the other battery.
DE 10 2010 062 249 A1 discloses an apparatus for use in an electrical drive system of a motor vehicle with at least two battery systems having load outputs which are united into a common load output. The load output of each battery system can hereby be connected and disconnected at the common load output by means of a pre-load circuit.